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Book of Abstracts: Albany 2007

category image Albany 2007
Conversation 15
June 19-23 2007

Structural and functional studies of non-coding RNAs

The vast majority of DNA in higher organisms does not code for proteins. Nevertheless, most of this DNA is transcribed into RNA. These non-coding RNAs are increasingly being found to have a wide range of biological functions, including roles in regulation of translation and transcription, splicing, replication of chromosome ends, nucleotide modification, and catalysis. We have been investigating the structure and function of RNA in telomerase and H/ACA RNPs.

Telomeres are the physical ends of linear chromosomes, and are composed of a 1000s of repeats of a short G-rich (in one strand) sequence of DNA and associated proteins. These sequences can form G-quadruplexes, which need to be unraveled for replication by telomerase, a large riboprotein complex that maintains the ends of telomeres. Telomerase uses an integral RNA template and a specialized reverse transcriptase to processively synthesize the G-rich strand. Telomerase has only a low or undetectable level of activity in normal somatic cells, but is up-regulated in most cancers, and is thus of interest as a target for anticancer drugs. In addition, mutations in the telomerase RNA have been found to cause some forms of the genetic diseases dyskeratosis congenita and aplastic anemia. Human telomerase is a large riboprotein complex that contains a 451 nt RNA along with a variety of proteins besides the telomerase reverse transcriptase. Results on the structure of domains of the RNA component of telomerase, and how mutations in the RNA affect the structure, thermodynamics, and function of telomerase, will be presented.

During the biogenesis of eukaryotic ribosomal RNA (rRNA) and spliceosomal small nuclear RNA (snRNA), uridines at specific sites are converted to pseudouridines by H/ACA ribonucleoprotein particles (RNPs). Each H/ACA RNP contains a substrate-specific H/ACA RNA and four common proteins, the pseudouridine synthase Cbf5, Nop10, Gar1, and Nhp2. In general, the H/ACA RNA contains two pseudouridylation (ψ) pocket, one or both of which are complimentary to the sequences flanking the target uridine. However, some H/ACA RNPs, e.g. this domain in telomerase, do not appear to play a role in guiding pseudouridylation. Results on our structural studies of the H/ACA RNAs will be presented.

References and Footnotes
  1. C.A. Theimer, L.D. Finger, L. Trantirek, and J. Feigon: ?Mutations linked to dyskeratosis congenita cause dynamic changes in telomerase RNA structure?, Proc. Natl. Acad. Sci. USA 100, 449 (2003).
  2. C.A. Theimer, L.D, Finger, and J. Feigon: ?YNMG tetraloop formation by a dyskeratosis congenita mutation in human telomerase RNA?, RNA 9, 1446-1455 (2003).
  3. C.A. Theimer, C.A. Blois, and J. Feigon: ?Structure of the human telomerase RNA pseudoknot reveals conserved tertiary interactions essential for function?, Mol. Cell 17, 671 (2005).
  4. M. Khanna, H. Wu, C. Johansson, M. Caizergues-Ferrer, and J. Feigon: ?Structural studies of the H/ACA snoRNP components Nop10p and the 3? hairpin of U65 snoRNA?, RNA 12, 42 (2006).
  5. R.J. Richards, C.A. Theimer, L.D. Finger, and J. Feigon: ?Structure of the Tetrahymena thermophila telomerase RNA helix II template boundary element? Nucleic Acids Res. 34, 816 (2006).
  6. C.A. Theimer and J. Feigon: ?Structure and function of telomerase RNA? Curr. Opin. Struct. Biol. 16, 307 (2006).
  7. R.J. Richards, H. Wu, L. Trantirek, C.M. O?Connor, K. Collins, and J. Feigon: ?Structural study of elements of Tetrahymena telomerase RNA stem-loop IV domain important for function? RNA, 12, 1475 (2006).

Juli Feigon

Department of Chemistry and Biochemistry, P.O. Box 951569, Univdersity of California, Los Angeles, CA 90095-1569

Phone: 310 206 6922
Fax: 310 825 0982
Email: feigon@mbi.ucla.edu